A fluorescence microscope is an optical microscope 
  that uses fluorescence and phosphorescence instead of, 
     or in addition to, reflection and absorption to study  
  .                                  organic or inorganic substances
                                        
  Fluorescence is the emission of light by a substance 
  that has absorbed light or other electromagnetic 
  .radiation
  The fluorescence microscope was devised in the early 
   part of the twentieth century by August Köhler, Carl 
   Reichert, and Heinrich Lehmann.     
  Principle of Fluorescence Microscopy 
  Most cellular components are colorless and 
  cannot be clearly distinguished under a 
  microscope. The basic premise of fluorescence 
  .microscopy is to stain the components with dyes
  Fluorescent dyes, also known as fluorophores or  
  fluorochromes, are molecules that absorb 
  excitation light at a given wavelength (generally 
  UV), and after a short delay emit light at a longer 
  . wavelength
    The emission light can then be filtered from the 
      excitation light to reveal the location of the 
      fluorophores.
    Fluorescence microscopy uses a much higher 
      intensity light to illuminate the sample. This 
      light excites fluorescence species in the sample, 
      which then emit light of a longer wavelength.
    The image produced is based on the second light 
    source or the emission wavelength of the 
    fluorescent species rather than from the light 
    originally used to illuminate, and excite, the 
    sample
    Parts of Fluorescence Microscope         
    Fluorescent dyes (Fluorophore)- 1    
       A fluorophore is a fluorescent chemical compound that 
        can re-emit light upon light excitation.
       Fluorophores typically contain several com
       bined aromatic groups, or plane or cyclic molecules 
        with several π bonds.
       Many fluorescent stains have been designed for a range 
        of biological molecules.
       Some of these are small molecules that are intrinsically 
        fluorescent and bind a biological molecule of interest. 
        Major examples of these are nucleic acid stains like 
        DAPI and Hoechst, phalloidin which is used to stain 
        actin fibers in mammalian cells.